This thesis addresses the characterisation of these advanced photomasks. There are many techniques published that produce advanced masks, but this work deals with two of the primary ones, advanced binary masks and alternating phase shift masks (altPSM). The work covered studies the methods of extracting the three dimensional structure of these masks and uses simulation to show what effect this has upon the waves propagating through them. The thesis deals with the way in which mask inspection systems image masks and the differences inherent between the way they observe defects and the way that these defects are reproduced when printed on IC patterns. This is a vitally important component of manufacturing as the inspection tool must be calibrated to replicate a much more complex and expensive exposure tool. It is shown through simulation that smaller defects at the centre of a space rather than at the edge result in the limits of CD tolerance being reached and that the most sensitive position for a defect is not at the edge or centre of the space but rather at a position between these two. With imaging close to the theoretic limits, there is a non linear transfer of dimensional errors to the wafer. This makes it vitally important that the actual dimension on the photomask is known and on target. However the dimensions on these masks are below those normally imaged by conventional optical dimension measurement systems. The alternative used on wafers, that of scanning electron microscopy (SEM) is not reliable on masks as they have a conducting surface on an insulator. This very structure does however make them suitable for measurement with novel electrical structures. The thesis explores the potential of this technique and compares its accuracy to that of conventional optical and SEM systems showing a 99% correlation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:666100 |
| Date | January 2006 |
| Creators | McCallum, Martin |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/15319 |
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